Method of Manufactring Ring-Shaped Member

ABSTRACT

The yield rate or the percentage of the weight of the ring-shaped member with respect to the weight of the raw material and the yield rate or the percentage of the ring-shaped member with respect to the blank are improved to achieve the cost reduction. A half-finished article  18  having large curved parts  3 D obtained by widening the curved parts  3   d  so as to have a curvature radius larger than the initial curvature radius, and bulge-out parts  3 E curved to a circular arc shape at a curvature radius larger than the curvature radius of the curved parts  3   d  at the linear parts  3   b   , 3   c  is molded, and thereafter, the half-finished article  18  is molded into an annular shape to obtain the ring-shaped member  1.

TECHNICAL FIELD

The present invention relates to a method of manufacturing a ring-shapedmember.

BACKGROUND ART

A ring-shaped member 1 as shown in FIG. 12 has been conventionallymanufactured through a method of punching out a plurality of annularring-shaped members 1 by one column or a plurality of columns by apressing device from a raw material 2 having a predetermined platethickness as shown in FIGS. 13( a) and 13(b).

However, in the conventional manufacturing method, the yield rate or thepercentage of the weight of the ring-shaped member 1 with respect to theweight of the raw material 2 is bad, and tends to increase the cost ofthe ring-shaped member 1.

This is because the material is removed at high percentage of skeletonS1 and slug S2 with respect to the ring-shaped member 1. The “Skeleton”is a frame shaped scrap that remains after punching out a plurality ofring-shaped members 1, and the “slug” is a plurality of scraps punchedout and removed with a punch when punching out the plurality ofring-shaped members 1.

A method of molding the ring-shaped member shown in FIGS. 14( a) and14(b) has thus been proposed (patent document 1).

The method of molding the ring-shaped member described in a patentdocument 1 includes a step of continuously bending the width of anelliptical ring-shaped raw material into a circular shape whilepreventing the deformation thereof, and a step of making the rawmaterial formed into a circular shape into a perfect circle.

That is, as shown in FIG. 14( a), inner and outer rollers 103, 104 thatfreely rotate and move so as to slidably hold in between one width onthe minor side of the elliptical ring-shaped raw material 100, and apair of freely movable bending rollers 105 are arranged, where the innerand outer rollers 103, 104 are rotated in a direction of an arrow F orin the opposite direction thereof to push the pair of bending rollers105 in the direction of an arrow G while feeding the ellipticalring-shaped raw material 100 in the direction of an arrow L or in theopposite direction thereof, thereby sequentially performing thecurvature process on the linear portion of the raw material 100 to bemolded into a raw material 101 of circular shape.

Thereafter, as shown in FIG. 14( b), a large diameter inner roller 106is externally fitted to the inner roller 103 so as to be simultaneouslyrotatable and inscribed to the raw material 101 formed into a circularshape, and the large diameter inner roller 106 and the outer rollers103, 104 are rotated in the direction of the arrow F or in the oppositedirection thereof to obtain a ring-shaped member 102 molded to a perfectcircle.

According to such method of molding the ring-shaped member, the rawmaterial 101 of circular shape is obtained from the ellipticalring-shaped member 100, and thus the material can be removed such thatthe percentage of the skeleton and the slug with respect to thering-shaped member 102 of a perfect circle is suppressed lower than thepercentage of the skeleton S1 and the slug S2 with respect to thering-shaped member 1 described in FIG. 13, thereby improving the yieldrate or the percentage or the weight of the ring-shaped member 102 withrespect to the weight of the raw material, and the cost of thering-shaped member 102 can be removed.

Patent document 1: Japanese Patent Application Laying-open No. 62-203633

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, in the method of molding the ring-shaped member described inthe patent document 1, a curved part 107 having a small curvature radiusremaining on the circular shaped raw material 101 is pressed and widenedfrom the inner side with a strong pressing force in the direction of anarrow K by the large diameter inner roller 106. When the curved part 107of small curvature radius is pressed and widened from the inner side, alarge “extension” is generated at the radial inner region of smallcurvature radius in the curved part 107 thereby thinning the relevantregion and concentrating stress. Therefore, cracks may be generated atthe radial inner region of the curved part 107 in the process of moldingthe circular shaped raw material 101 into a perfect circular shapedring-shaped member 102, which degrades the yield rate or the percentageof the perfect circular shaped ring-shaped member 102 with respect tothe elliptical ring-shaped raw material 100, and increases the cost.

The present invention, in view of solving the above problems, aims toprovide a method of manufacturing a ring-shaped member that improves theyield rate or the percentage of the weight of the ring-shaped memberwith respect to the weight of the raw material, and improves the yieldrate or the percentage of the ring-shaped member (correspond toring-shaped part molded into a perfect circle described in the patentdocument 1) with respect to a longitudinal annular blank (correspond toelliptical ring-shaped raw material described in the patent document 1),even though the method can achieve a cost reduction.

Means for Solving the Problems

The present invention relates to a method of manufacturing a ring-shapedmember in which an annular ring-shaped member is obtained from alongitudinal annular blank having curved parts at both ends in alongitudinal direction, wherein the longitudinal annular blank is moldedto a half-finished article having a pair of large curved parts widenedso as to have a curvature radius larger than the curvature radius of thecurved parts and a pair of bulge-out parts curved to a circular arcshape at a curvature radius larger than the curvature radius of thecurved parts, and thereafter, the half-finished article is molded intothe annular ring-shaped member.

According to such configuration, the annular ring-shaped member isobtained from the longitudinal annular blank, and thus the material canbe removed such that the percentage of the skeleton and the slug withrespect to the ring-shaped member is suppressed low compared to the caseshown in FIG. 13, and the yield rate or the percentage of the weight ofthe ring-shaped member with respect to the weight of the raw materialcan be improved.

Prior to molding the longitudinal annular blank into an annular shape, ahalf-finished article including a pair of large curved parts having acurvature radius larger than the curvature radius of the curved partsand a pair of bulge-out parts curved to a circular shape at a curvatureradius larger than the curvature radius of the curved parts is molded inadvance, and such half-finished article is molded into an annularring-shaped member, and thus “extension” of the radial inner region ofthe large curved parts and the bulge-out parts having a large curvatureradius is suppressed as much as possible, the thinning of the thicknessof the radial inner region is avoided, and stress concentration of theradial inner region is alleviated when molding the half-finished articleinto an annular shape. As a result, cracks are not generated at thelarge curved parts and the bulge-out parts, and the yield rate or thepercentage of the ring-shaped member with respect to the longitudinalannular blank can be improved.

The present invention relates to a method of manufacturing a ring-shapedmember in which an annular ring-shaped member is obtained from alongitudinal annular blank, wherein the longitudinal blank has linearparts facing each other at both sides in the width direction and a pairof curved parts for continuing both ends in the longitudinal directionof the linear parts; and the blank is molded into a blank having adimension in the width direction widened from the dimension in the widthdirection of the blank by widening the linear parts outward in the widthdirection, the blank whose dimension is widened in the width directionis molded into a half-finished article having a pair of large curvedparts obtained by widening the curved parts so as to have a curvatureradius larger than the initial curvature radius and a pair of bulge-outparts curved into a circular arc shape at a curvature radius larger thanthe curvature radius of the curved parts at the linear parts, andthereafter, the half-finished article is molded to the annularring-shaped member.

According to such configuration, the annular ring-shaped member isobtained from the longitudinal annular blank, and thus the material canbe removed such that the percentage of the skeleton and the slug withrespect to the ring-shaped member is suppressed low compared to the caseshown in FIG. 13, and the yield rate or the percentage of the weight ofthe ring-shaped member with respect to the weight of the raw materialcan be improved.

Prior to molding the longitudinal annular blank into an annular shape, astep of molding into a half-finished article including large curvedparts obtained by widening the curved parts so as to have a curvatureradius larger than the initial curvature radius and bulge-out partscurved to a circular arc shape at a curvature radius larger than thecurvature radius of the curved parts at the linear parts is performedafter the step of widening the linear parts outward in the widthdirection and molding into a blank of dimension in the width directionwider than the dimension in the width direction of the blank, and thus“extension” of the radial inner region of small curvature radius at thecurved parts is suppressed as much as possible, thinning the radialinner region is avoided, and stress concentration of the radial innerregion is alleviated in the step of molding to the half-finishedarticle, whereby the curved parts are readily molded into the largecurved parts of large curvature radius without generating cracks at thecurved parts.

After the step of molding to the half-finished article, thehalf-finished article is molded into an annular ring-shaped member, andthus “extension” of the radial inner region of the large curved partsand the bulge-out parts having a large curvature radius is suppressed asmuch as possible, thinning the radial inner region is avoided, andstress concentration of the radial inner region is alleviated whenmolding into an annular shape. As a result, cracks are not generated atthe large curved parts and the bulge-out parts, and the yield rate orthe percentage of the ring-shaped member with respect to thelongitudinal annular blank can be improved.

EFFECTS OF THE INVENTION

According to the present invention, the yield rate or the percentage ofthe weight of the ring-shaped member with respect to the weight of theraw material is improved by removing the material such that thepercentage of the skeleton and the slug with respect to the ring-shapedmember is suppressed low, and the cost of the ring-shaped member can bereduced. Furthermore, “extension” of the radial inner region at thecurved parts of the longitudinal annular blank is suppressed as much aspossible, thinning the radial inner region can be avoided, and stressconcentration of the radial inner region is alleviated, whereby cracksare not generated at the curved parts of the longitudinal annular blank,and the yield rate or the percentage of the ring-shaped member withrespect to the longitudinal annular blank can be advantageouslyimproved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a first embodiment of a step of punchingout blanks from a raw material.

FIG. 2 is an enlarged front view showing the blank punched out from theraw material of FIG. 1.

FIG. 3 is a plan view showing an embodiment of a state in which theblank is set in a first shaping device.

FIG. 4 is a plan view showing an embodiment of a state in which thedeformed blank is molded by the first shaping device.

FIG. 5 is a plan view showing an embodiment of a state in which thedeformed blank is set in a second shaping device.

FIG. 6 is a plan view showing an embodiment of a state in which ahalf-finished article is molded by the second shaping device.

FIG. 7 is a plan view showing an embodiment of a state in which thehalf-finished article is set in a third shaping device.

FIG. 8 is a plan view showing an embodiment of a state in which theright half portion of the half-finished article is molded into asemicircle by the third shaping device.

FIG. 9 is a plan view showing an embodiment of a state in which thehalf-finished article is molded into a ring-shaped member by the thirdshaping device.

FIG. 10 is an enlarged front view showing a second embodiment of ablank.

FIG. 11 is a plan view showing another embodiment of a step of punchingout the blank from the raw material.

FIG. 12 is a front view showing one example of the ring-shaped member.

FIG. 13 is a plan view showing the conventional steps of punching outthe blank from the material, where 13(a) shows punching out one column,13(b) shows punching out in parallel.

FIG. 14 is an explanatory view of a method of molding the ring-shapedmember described in the patent document 1.

DESCRIPTION OF NUMERAL REFERENCES

-   1 ring-shaped member-   3 longitudinal annular blank-   3 b, 3 c linear part-   3A blank which width dimension is widened-   3D large curved part-   3 d curved part-   3E bulge-out part-   18 half finished-article

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the method of manufacturing the ring-shapedmember according to the present invention will now be described based onthe drawings.

As shown in FIG. 1, a plurality of longitudinal annular blanks 3 ispunched out in series at a predetermined spacing 1 in the feedingdirection by the pressing device while feeding the raw material 2 of apredetermined plate thickness in the longitudinal direction of the rawmaterial 2 as shown by an arrow X. The raw material 2 used may be thatformed in to a plate shaped body by rolling the metal rod material suchas copper, aluminum, iron, stainless steel and the like, or that formedas a plate shaped body from the beginning. The longitudinal annularblank 3 may be obtained by performing press work such as cutting andpunching, casting and the like on the metal rod material instead ofbeing obtained by punching out the raw material 2 of plate shaped body.

The longitudinal annular blank 3 includes linear parts 3 b, 3 c on theleft and right sides facing each other so as to sandwich a longitudinalhole 3 a having a small width dimension w1 on the inner side, and a pairof curved parts 3 d continuing both ends in the longitudinal directionof the linear parts 3 b, 3 c, as shown in FIG. 2, and the longitudinalannular blank 3 is set in a first shaping device 4, as shown in FIG. 3.

The first shaping device 4 includes a moving plate 5 and a pair of frontand back guide plates 6, where the moving plate 5 is guided by the guideplates 6 to move forward and backward in the left and right direction(direction of arrow X1, X2) by a forward/backward movement mechanism(not shown). The moving plate 5 includes a main body part 5 a, andcollar parts 5 b, 5 b formed on both ends in the front and backdirection of the main body part 5 a, where the collar parts 5 b, 5 bslidably go under the lower side of the edges 6 a, 6 a at the sidefacing the opponent in the guide plate 6, and a vertical step differencesurface 5 c formed at the boundary of the main body part 5 a and thecollar parts 5 b, 5 b is arranged so as to slidably contact the endsurface 6 b at the side facing the opponent in the guide plate 6. Aninner die 8-1 having a boat shape in a projected plane is projectedupward at the central part of the main body part 5 a in the moving plate5 on the line Y orthogonal to line X. The width dimension w2 of theinner die 8-1 is set to a size slightly smaller than the width dimensionw1 of the longitudinal hole 3 a so as to fit into the longitudinal hole3 a of the blank 3.

A pair of front and back positioning projections 8-2, and two pairs offront and back positioning/deformation tolerating projections 9 arearranged on the guide plate 6 in the first shaping device 4. Asmentioned below, the pair of positioning projections 8-2 is provided toprevent the longitudinal annular blank 3 from moving in the direction ofthe arrow Y1, Y2 and to position the longitudinal annular blank 3 at anappropriate position when the longitudinal annular blank 3 is set in thefirst shaping device 4, and furthermore, is arranged at symmetricalpositions with the line X in between so as to face each other on theline Y orthogonal to the line X, where the distance in between is set toa value slightly larger than the dimension in the longitudinal directionof the longitudinal annular blank 3 to enable the setting of thelongitudinal annular blank 3.

As mentioned below, the two pairs of front and backpositioning/deformation tolerating projections 9 are provided to preventthe longitudinal annular blank 3 from moving in the direction of thearrows X1, X2 and to position the longitudinal annular blank 3 at anappropriate position as well as to tolerate the deformation of thelongitudinal annular blank 3 by an inner die 8-1 when the longitudinalannular blank 3 is set in the first shaping device 4, and is furtherarranged at symmetrical positions with the line X and the line Y passingthrough the center of the moving plate 5 in between, where the distancein between in the direction of the line X is set at a value slightlylarger than the dimension in the width direction of the longitudinalannular blank 3 to enable the setting of the longitudinal annular blank3. Each positioning/deformation tolerating projection 9 has a circulararc shaped deformation tolerating surface 9 b formed in continuation tothe positioning surface 9 a that is parallel to the line Y.

As shown in FIG. 3, when the longitudinal annular blank 3 is set in thefirst shaping device 4, an upper die 10 shown by a double-chain dashedline is lowered from above. The upper surfaces of the guide plate 6, thepositioning projection 8-2, and the positioning/deformation toleratingprojection 9 are thereby pressed by the lower surface of the upper die10, and the upper surfaces of the blank 3 and the inner die 8-1 face thelower surface of the upper die 10 by way of an extremely small gap(small gap allowing slide movement) thereby preventing a warp of theblank 3.

The moving plate 5 is moved in the direction of the arrow X2 in thisstate. The inner die 8-1 presses and energizes the linear part 3 c onthe right side of the longitudinal annular blank 3 in the direction ofthe arrow X2 from the inner side to bend in the direction of the arrowX2 as shown in FIG. 4, and subsequently, the moving plate 5 is moved inthe direction of the arrow X1 so that the inner die 8-1 presses andenergizes the linear part 3 b on the left side (see FIG. 3) of thelongitudinal annular blank 3 in the direction of the arrow X1 from theinner side to bend in the direction of the arrow X1 as shown in FIG. 4,where a longitudinal annular blank 3A in which the dimension in thewidth direction is widened and deformed from the dimension in the widthdirection of FIG. 3 is molded. In the process of molding, the wideningdeformation of the linear parts 3 b, 3 c on both left and right sides ofthe longitudinal annular blank 3 shown in FIG. 3 is tolerated since theouter surface in the width direction of the region near the curved part3 d of the linear parts 3 b, 3 c is widened until contacting thecircular arc shaped deformation tolerating surface 9 b of each of thetwo pairs of positioning/deformation tolerating projection 9, andthinning the widened and deformed part in time of widening deformationcan be suppressed since the deformation tolerating surface 9 b is formedinto a circular arc shape.

In the next step, the deformed longitudinal annular blank 3A shown inFIG. 4 is set in a second shaping device 11 shown in FIG. 5.

The second shaping device 11 includes a pair of left and right moldingouter dies 12, and a pair of front and back regulating dies 13, wherethe molding outer die 12 is guided by a guide groove 14 and is movedforward and backward in the left and right direction (direction ofarrows X1, X2) on the base 15 by a forward/backward movement mechanism(not shown).

The molding outer die 12 includes a mounting surface 12 a and a pressingsurface 12 b projecting vertically upward from the mounting surface 12 aand having the projected plane which is depressed into a circular arcshape, where the curvature radius of the pressing surface 12 b is set toa value larger than the curvature radius of the outer peripheral surfaceof the curved part 3 d in the deformed longitudinal annular blank 3A.The regulating die 13 is formed at the end face on the side facing theopponent with a regulating surface 13 a having the projected plane whichis depressed into a circular arc shape. Furthermore, a holding inner die16 projecting upward from the upper surface at the central part of thebase 15 and having a boat shape in projected plane view is arrangedextending in the direction of the line X, where the width dimension ofthe holding inner die 16 is set to a dimension slightly smaller than thewidth dimension of the longitudinal hole 3 e so as to be fitted to thelongitudinal hole 3 e of the deformed longitudinal annular blank 3A. Acircular arc shaped holding surface 16 a is arranged vertically at bothends on the line X of the holding inner die 16, and a cut-out part 16 bis formed on the lower side of the holding surface 16 a and the vicinitythereof.

As shown in FIG. 5, after the longitudinal annular blank 3A is set inthe second shaping device 11 with the holding inner die 16 sandwiched bythe linear parts 3 b, 3 c of the deformed longitudinal annular blank 3Aand the curved part 3 d and the vicinity of the blank 3A mounted on themounting surface 12 a of the molding outer die 12, an upper die 17 shownby a double chain-dashed line is lowered from above. As a result, theupper surfaces of the regulating die 13 and the holding inner die 16 arepressed by the lower surface of the upper die 17, and the upper surfacesof the longitudinal annular blank 3A and the molding outer die 12 facethe lower surface of the upper die 17 by way of an extremely small gap(small gap allowing slide movement) thereby preventing the warp of theblank 3A.

The molding outer dies 12 are moved in the direction of the arrows X1,X2 in this state. The pressing surface 12 b of the molding outer die 12thereby presses and energizes the outer side of the curved part 3 d ofthe deformed longitudinal annular blank 3A towards the curved part 3 don the opponent side. In this case, the mounting surface 12 a of themolding outer die 12 enters the cut-out part 16 b of the holding innerdie 16. Therefore, as shown in FIG. 6, both curved parts 3 d aredeformed along the pressing surface 12 b when the radial outer surfaceof large curvature radius is pressed inward from the outer side by thepressing surface 12 b depressed into a circular arc shape of the moldingouter die 12 in a state wherein the radial inner surface is slightlypressed and widened by the circular arc shaped holding surface 16 a ofthe holding inner die 16 and positioned with the movement in thedirections of the arrows X1, X2 regulated, thereby molding into a largecurved part 3D having a curvature radius which is larger than thecurvature radius of the curved parts 3 d, and thus “extension” isgenerated in the radial outer region of the large curved part 3D havinglarge curvature radius and “extension” in the radial inner region issuppressed as much as possible, thinning the radial inner region isavoided, and furthermore, flow of material that thickens the largecurved part 3D is generated so as to alleviate stress concentration atthe radial inner region. As a result, both curved parts 3 d can bemolded to the large curved part 3D having a larger curvature radius thanthe initial curvature radius and being advantageous in manufacturing thering-shaped member 1 without generating cracks at the curved part 3 d,and thus the yield rate or the percentage of the ring-shaped member 1with respect to the longitudinal annular blank 3A can be improved.

In the process of molding into the large curved part 3D having acurvature radius larger than the curvature radius of both curved parts 3d, the linear parts 3 b, 3 c in the deformed longitudinal annular blank3A shown in FIG. 5 are widened in the direction of the arrows Y1, Y2thereby forming a pair of bulge-out-parts 3E curved to a circular arcshape at a curvature radius larger than the initial curvature radius ofthe curved part 3 d at the central part, as shown in FIG. 6, where thedeformed longitudinal annular blank 3A (see FIG. 5) is regulated fromwidening in excess in the direction of the arrows Y1, Y2 when the outersurface of the bulge-out part 3E contacts the regulating surface 13 adepressed into a circular arc shape of the regulating die 13, and ahalf-finished article 18 including a pair of large curved parts 3D oflarge curvature radius and a pair of bulge-out parts 3E curved to acircular arc shape at a large curvature radius, and having the largecurved parts 3D and the bulge-out parts 3E continued by way of fourshort linear parts 3F is molded.

The half-finished article 18 shown in FIG. 6 is further set in a thirdshaping device 19 shown in FIG. 7 in the next step.

The third shaping device 19 includes a base 20, and an upper plate 21for blocking the upper surface of the base 20 by way of a spacing in theheight direction, where a guide groove 22 is formed in the base 20 onthe line X passing through the center, and a moving plate 23 that freelymoves forward and backward in the direction of the arrows X1, X2 isfitted into the guide groove 22. The moving plate 23 moves forward andbackward in the direction of the arrows X1, X2 by a forward/backwardmoving mechanism (not shown). The upper surface of the moving plate 23is in plane with the upper surface of the base 20, and a finishing innerdie 24 having an elliptical shape in a projected plane view is arrangedat the central part so as to project upward on a line Y passing throughthe center of the base 20 and being orthogonal to the line X. Thefinishing inner die 24 faces a window part 25 of a substantially perfectcircle formed on the upper plate 21, and the inner peripheral surface ofthe window part 25 functions as an outer die.

As shown in FIG. 7, when the half-finished article 18 is set in thethird shaping device 19, an upper die 26 shown with a doublechain-dashed line is lowered from above. The upper surface of the upperplate 21 is thereby pressed by the lower surface of the upper die 26,and the upper surfaces of the half-finished article 18 and the finishinginner die 24 face the lower surface of the upper die 26 by way of anextremely small gap (small gap allowing slide movement) therebypreventing the warp of the half-finished article 18.

The moving plate 23 is moved in the direction of the arrow X2 in such astate. As a result, the finishing inner die 24 presses and energizes theright half portion of the half-finished article 18 in the direction ofthe arrow X2 from the inner side and presses the outer peripheralsurface of the right half portion against the inner peripheral surfaceof the right half portion in the window part 25 of a substantiallyperfect circle, as shown in FIG. 8, thereby molding the right halfportion of the half-finished article 18 into a semicircle. Subsequently,the moving plate 23 is moved in the direction of the arrow X1. Thefinishing inner die 24 thereby presses and energizes the left halfportion of the half-finished article 18 in the direction of the arrow X1from the inner side and presses the outer peripheral surface of the lefthalf portion against the inner peripheral surface of the left halfportion in the window part 25 of a substantially perfect circle as shownin FIG. 9, thereby molding the left half portion of the half-finishedarticle 18 into a semicircle to manufacture a ring-shaped member 1 shownin FIG. 9 and FIG. 12. In molding the half-finished article 18 into anannular ring-shaped member 1, “extension” in the radial inner region ofthe large curved part 3D and the bulge-out part 3E having a largecurvature radius is suppressed as much as possible, thinning of theradial inner region is avoided, and concentration of stress on theradial inner region is alleviated. As a result, cracks are not generatedat the large curved part 3D and the bulge-out part 3E.

Therefore, according to the present invention, the ring-shaped member 1shown in FIG. 9 and FIG. 12 is manufactured by punching out a pluralityof longitudinal annular blanks 3 from a raw material 2 shown in FIG. 1,and pressing and widening the longitudinal annular blanks 3 to be moldedinto an annular shape by first to third shaping devices 4, 11, 19.Therefore, the yield rate or the percentage of the weight of thering-shaped member 1 with respect to the weight of the raw material 2can be improved, and the cost of the ring-shaped member 1 can be reducedby removing the material such that the percentage of the skeleton S1 andthe slug S2 of FIG. 1 with respect to the ring-shaped member 1 issuppressed lower than the percentage of the skeleton S1 and the slug S2with respect to the ring-shaped member 1 described in FIG. 13.

Furthermore, each curved part 3 d is deformed along the pressing surface12 b and molded into the large curved part 3D of large curvature radiuswhen the radial outer surface is pressed inward from the outer side bythe pressing surface 12 b depressed into a circular arc shape of themolding outer die 12 with the radial inner surface slightly pressed andwidened by the circular arc shaped holding surface 16 a of the holdinginner die 16 and positioned with the movement in the directions of thearrows X1, X2 regulated by pressing and energizing the outer side of thepair of curved parts 3 d of the deformed longitudinal annular blank 3Atowards the curved part 3 d on the opponent side by the pressing surface12 b depressed to a circular arc shape of the molding outer die 12 bythe second shaping device 11, and thus “extension” in the radial outerregion having large curvature radius is suppressed as much as possible,thinning the radial inner region is avoided, and furthermore, flow ofmaterial that thickens the large curved part 3D is generated andalleviates stress concentration at the radial inner region. As a result,both curved parts 3 d can be molded into a large curved part 3D having alarge curvature radius and being advantageous in manufacturing thering-shaped member 1 without generating cracks at the curved part 3 d,and thus the yield rate or the percentage of the ring-shaped member 1with respect to the longitudinal annular blank 3A can be improved andthe cost of the ring-shaped member 1 can be reduced.

In the above embodiment, the longitudinal annular blank 3 having a smallwidth dimension w1 of the longitudinal hole 3 a is punched out, and suchblank 3 is pressed and widened to manufacture the ring-shaped member 1,as shown in FIG. 2, but as shown in FIG. 10, a longitudinal annularblank 27 having a longitudinal hole 27 a of oval shape in which thewidth dimension w3 is sufficiently larger than the width dimension w1 ofFIG. 2 may be punched out, and such blank 27 may be pressed and widenedthrough the same procedures as the above embodiment to be molded intothe ring-shaped member 1. In this case as well, the yield rate or thepercentage of the ring-shaped member 1 with respect to the longitudinalannular blank 27 can be improved and the cost of the ring-shaped member1 can be reduced, similar to the above embodiment.

Moreover, in punching out a plurality of longitudinal annular blanks 3,27 from the raw material 2 of a predetermined width, the outer end facesof the linear parts 3 b, 3 c in the longitudinal annular blank 3, 27 maybe formed using both ends faces 2 a in the width direction of the rawmaterial 2, and the raw material 2 may be cut by the pressing device toform a pair of curved parts 3 d continuing the pair of linear parts 3 b,3 c to each other at both ends in the longitudinal direction, as shownin FIGS. 11( a) and 11(b). Therefore, the material can be removed suchthat the percentage of scraps with respect to the longitudinal annularblanks 3, 27 is suppressed to a minimum. In other words, the scraps arereduced to the slug S1 punched out and removed by punch in time ofpunching out the longitudinal hole 3 a or the longitudinal hole 27 a ofoval shape, and an end plate part 2 x of drum shape existing between thelongitudinal annular blanks 3 or blanks 27 arrayed in the longitudinaldirection and to be separated away from the raw material 2. As a result,the yield rate or the percentage of the weight of the ring-shaped member1 with respect to the weight of the raw material 2 further can beimproved.

The method of manufacturing the ring-shaped member of the presentinvention also has the following features.

The longitudinal annular blank 3 is molded to an annular shape bypressing the curved part 3 d at both ends in the longitudinal directiontowards the opponent side from the outer side. The material can beremoved such that the percentage of the skeleton and the slug withrespect to the ring-shaped member 1 is suppressed low, and the yieldrate or the percentage of the weight of the ring-shaped member 1 withrespect to the weight of the raw material can be improved. Furthermore,since the curved parts 3 d at both ends in the longitudinal directionare pressed towards the opponent side from the outer side, the“extension” of the radial inner region having a small curvature radiusat the curved part 3 d can be suppressed as much as possible, thinningof the radial inner region is avoided, and furthermore, the flow ofmaterial that thickens the curved part 3 d is generated and alleviatesthe stress concentration of the radial inner region. As a result, cracksare not generated at the curved part 3 d, and the yield rate or thepercentage of the ring-shaped member 1 with respect to the longitudinalannular blank 3 can be improved.

The longitudinal annular blank 3 is desirably molded into an annularshape by shaping devices 11, 19 including an inner die 16, 24 and anouter die 12, 25. The ring-shaped member 1 of high quality is therebyefficiently manufactured and cost can be reduced.

Moreover, the longitudinal annular blank 3 includes linear parts 3 b, 3c facing each other at both sides in the width direction with thelongitudinal hole 3 a on the inner side, and curved parts 3 d forcontinuing both ends in the longitudinal direction of the linear parts 3b, 3 c, where the dimension in the width direction of the longitudinalannular blank 3 is widened by pressing and energizing the linear parts 3b, 3 c by the inner die 8-1 fitted in the longitudinal hole 3 a, andthereafter, the outer side of the curved parts 3 d is pressed andenergized towards the curved part 3 d on the opponent side with themolding outer die 12 with the holding inner die 16 fitted into thelongitudinal hole 3 a whose dimension in the width direction is widened,thereby pressing and widening the curved parts 3 d to large curved parts3D having a large curvature radius.

Therefore, after widening the dimension in the width direction of thelongitudinal annular blank 3 by the inner die 8-1 fitted into thelongitudinal hole 3 a and pressing and energizing the outer side of thecurved part 3 d toward the curved part 3 d on the opponent side by themolding outer die 12 with the holding inner die 16 fitted into thelongitudinal hole 3 a whose dimension in the width direction is widened,the curved parts 3 d are pressed inward from the outer side by themolding outer die 12 while being positioned with the movement towardsthe curved part 3 d on the opponent side regulated by the holding innerdie 16, whereby “extension” of the radial inner region having a smallcurvature radius in the curved part 3 d is suppressed as much aspossible, thinning of the radial inner region is avoided, and stressdoes not concentrate at the radial inner region, so that both curvedparts 3 d are readily molded into the large curved parts 3D having alarge curvature radius without generating cracks at the curved parts 3d.

1. A method of manufacturing a ring-shaped member in which an annularring-shaped member is obtained from a longitudinal annular blank havingcurved parts at both ends in a longitudinal direction, wherein thelongitudinal annular blank is molded into a half-finished article havinga pair of large curved parts widened so as to have a curvature radiuslarger than the curvature radius of the curved parts and a pair ofbulge-out parts curved to a circular arc shape at a curvature radiuslarger than the curvature radius of the curved parts, and thereafter,the half-finished article is molded into the annular ring-shaped member.2. A method of manufacturing a ring-shaped member in which an annularring-shaped member is obtained from a longitudinal annular blank,wherein the longitudinal annular blank has linear parts facing eachother at both sides in the width direction and a pair of curved partsfor continuing both ends in the longitudinal direction of the linearparts; and the blank is molded into a blank having a dimension in thewidth direction widened from the dimension in the width direction of theblank by widening the linear parts outward in the width direction, theblank whose dimension in the width direction is widened is molded into ahalf-finished article having a pair of large curved parts obtained bywidening the curved parts so as to have a curvature radius larger thanthe initial curvature radius and a pair of bulge-out parts curved into acircular arc shape at a curvature radius larger than the curvatureradius of the curved parts at the linear parts, and thereafter, thehalf-finished article is molded into the annular ring-shaped member.